1. Field of the Invention
The present invention relates to an improved surge protecting circuit for electronic products and, more particularly, to a surge protecting circuit which can protect the power source and the internal and external circuit elements of an electronic product by absorbing external surges through ground.
2. Description of the Related Art
Generally, since various electronic products such as televisions or video cassette recorders are connected to an antenna, they are subject to damage caused by external surges, such as lightning, which may conduct through the antenna to the electronic product. Therefore, there are certain safety measures which may be taken to protect the products from these external surges.
For example, referring to FIG. 1, an AC (alternating current) ground pattern 12 of an AC (alternating current) input circuit 10 of a conventional electronic product is grounded through an AC input node having a current path to ground, whereas a DC (direct current) ground pattern 22 of a DC operating circuit 20, which is operated by receiving power through a secondary winding of a transformer T from the AC input circuit 10, is electrically floated. Therefore, external surges received by the DC operating circuit 20 through an antenna are transmitted to the AC ground pattern 12 through the DC ground pattern 22 by an arc discharge between terminals 32 and 34 of a surge protecting pattern 30, and absorbed to the ground through the AC input node.
An arc discharge gap between the terminals 34 and 32 of the surge protecting pattern 30 is specified to a safety distance, which is typically 5 mm. The terminals 34 and 32 of the surge protecting pattern 30 should be separated from each other by the specified safety distance or more in order to prevent impulse noise generated from an AC power source from being transmitted to the DC operating circuit 20 through the arc discharge gap. Although this safety distance is effective to isolate the noise generated by the AC power source, it is not as effective to provide substantial protection against damage to the DC operating circuit from external surges.
Recently, due to the increasing use of components such as microprocessors and integrated circuits in electronic products, which components are more sensitive to electrical surges, the industry has demanded a more definite protection against such surges.